1. Field of the Invention
The present invention relates to a laser diode suitable in the case where a very low operating current is desired and a method of manufacturing the same.
2. Description of the Related Art
In a laser diode, in the case where a very low operation current (very low current consumption) is desired, in general, a design focusing on the efficiency of a guided wave in a resonator and featuring very high optical density is adopted. Thereby, while a reduction in the operating current is achieved, a disadvantage such as a large decline in surge withstand voltage becomes apparent, so it is necessary to handle the laser with extra care.
In particular, an InAlGaP-based red laser diode mounted in a portable game console or the like using a DVD (Digital Versatile Disk) as a medium has a structure in which current consumption is reduced to a minimum. Therefore, compared to a typical laser for replaying DVDs, low surge withstand voltage as one characteristic of the laser diode appears prominently. In some cases, the surge withstand voltage is reduced to approximately 10 V.
A decline in the surge withstand voltage depends on the material of a mirror film arranged on an end surface. As widely used materials of the mirror film, an Al2O3 single layer for a front end surface (a main emission end surface) and an Al2O3/a-Si multilayer film for a rear end surface are used. However, in the case where Al2O3/a-Si is used for the rear end surface in a red laser diode, a-Si slightly absorbs red light, so when a surge current or an overcurrent enters, the rear end surface becomes susceptible to damage. This cause's an impediment to the improvement in the surge withstand voltage.
Therefore, to improve the surge withstand voltage, changing the material of the mirror film on the rear end surface can be considered. More specifically, a method of using a material such as TiOx instead of a-Si can be considered (for example, refer to Japanese Unexamined Patent Application Publication No. 2000-164978).